THE CLASSIFICATION OF NATURAL AND ANTHROPOGENIC VEGETATION IN MADAGASCAR

VEGETATION CLASSIFICATION AND MAPPING IN MADAGASCAR

The classification of vegetation has been an important theme of
research in botany, ecology, geography, and other disciplines
throughout much of this century. In Madagascar, vegetation
classification began with Baron (1889), who recognized 3 regions,
based exclusively on floristic criteria, i.e., the distribution
of ca. 3,000 species whose ranges were reasonably well known at
that time. Baron's approach was based on chorology -- the study
of the geographic distribution of organisms (Turrill, 1958;
White, 1993).

Over the next 75 years botanists refined their understanding of
the Malagasy flora and vegetation. Starting with Viguier (1914), but especially Perrier de la Bâthie (1921) and later Humbert (1927, 1951, 1955) vegetation classification
and mapping became increasingly sophisticated, culminating in the
publication of Humbert and Cours Darne's (1965) map for the
"Carte Internationale du Tapis Végétale et des Conditions
Ecologiques" (Humbert and Cours Darne, 1965). Earlier maps had
showed estimates of the native vegetation that was thought to
occur before the arrival of humans on Madagascar; the 1965 map
attempted to depict the coverage of both natural and
anthropogenic vegetation as it existed in the late 1950s, based
on information from aerial photographs and detailed topographic
maps.

Faramalala (1988, 1995; Faramalala and Conservation
International, 1995) has refined the map further using modern GIS
technology, updating it with the interpretation of LANDSAT
satellite imagess from the 1970s, although she has continued to
follow Humbert's basic approach. Du Puy and Moat (in press)
have developed a simplified geology map of Madagascar, and have used it to reanalyze the
relationships between broad rock type categories and existing primary vegetation as
indicated on Faramalala's map. Their work shows the presence of unique
vegetation types associated with specific substrates, many of
which are currently unrepresented in the country's protected
areas system.

All of these classifications are based on a fundamental division
of the country into two distinct floristic and vegetational
regions that had first been proposed by Perrier de la Bâthie
(1921):

The Flore au vent (windward flora), later re-named the
Région de l'Est (Eastern Region), was considered to include
the areas that come under the direct influence of the moist
southeast trade winds, which produce moderate to very high
levels of orographic precipitation as they encounter the
mountains along the N-S axis of the island. The Eastern
region also included western extensions into moist areas in
the Sambirano, Isalo, and elsewhere.

The Flore sous le vent (leeward flora), now referred to as
the Région de l'Ouest (Western Region), and which also
includes the far North of the island, comes under the
influence of the drying effects of the trade winds as they
undergo adiabatic warming as they descend after crossing
over the central plateau.